Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Phys Rev Lett. 2019 Feb 8;122(5):057207. doi: 10.1103/PhysRevLett.122.057207.
We investigate the low-temperature magnetic properties of the molecule-based chiral spin chain [Cu(pym)(H_{2}O){4}]SiF{6}·H_{2}O (pym=pyrimidine). Electron-spin resonance, magnetometry and heat capacity measurements reveal the presence of staggered g tensors, a rich low-temperature excitation spectrum, a staggered susceptibility, and a spin gap that opens on the application of a magnetic field. These phenomena are reminiscent of those previously observed in nonchiral staggered chains, which are explicable within the sine-Gordon quantum-field theory. In the present case, however, although the sine-Gordon model accounts well for the form of the temperature dependence of the heat capacity, the size of the gap and its measured linear field dependence do not fit with the sine-Gordon theory as it stands. We propose that the differences arise due to additional terms in the Hamiltonian resulting from the chiral structure of [Cu(pym)(H_{2}O){4}]SiF{6}·H_{2}O, particularly a uniform Dzyaloshinskii-Moriya coupling and a fourfold periodic staggered field.
我们研究了基于分子的手性自旋链 [Cu(pym)(H_{2}O){4}]SiF{6}·H_{2}O（pym=pyrimidine）的低温磁性质。电子自旋共振、磁强计和比热测量揭示了交错 g 张量、丰富的低温激发谱、交错磁化率和磁场施加时出现的自旋能隙的存在。这些现象类似于以前在非手性交错链中观察到的现象，可以用正弦-戈登量子场论来解释。然而，在目前的情况下，尽管正弦-戈登模型很好地解释了比热随温度的变化形式，但间隙的大小及其测量的线性场依赖性与正弦-戈登理论并不相符。我们提出，差异是由于 [Cu(pym)(H_{2}O){4}]SiF{6}·H_{2}O 的手性结构导致的哈密顿量中的附加项引起的，特别是均匀的 Dzyaloshinskii-Moriya 耦合和四重周期交错场。
